Maeion malloey



To all whom it may concern.'

Be it known that I, MARION MA'LnoRY, a citizen of the United States, residing at 'Wichita,- in the county of Sedgwick and State of Kansasfhave invented certain new anduseful Improvements in Spark-Plugs;

yand I do declare the following tobe a full,

- same.

My invention has for its object to provide a spark plug Vwhose insulator is so constructed as to render short circuiting practically impossib-le unless the insulator is damaged. Vith theV foregoing general ob]ect in view,

' the invention resides in the novel features of construction to be hereinafter fully de-Y drawing which forms a part of this speciig cation and in which a longitudinal section of y part of the insulator in elevation, is shown.

In the drawing above briefly described, the numeral 1 designates a cylindrical metal shell externally threaded at its lower end as seen at 2 and by preference provided with a gasket 3 for fluid tight engagement with the engine cylinder, the upper end of the shell being formedwith a head 4e of a shape to be engaged by a wrench, said head having in its upper end a socket 5 into which the bore of the shell opens.

An insulator 6 is received throughout substantially half of its length in the shell 1 in slightly spaced relation tothe latter, the intermediate portion of said insulator having an annular shoulder 7 received in the socket 5 and preferably tapered inwardly on its upper side as shown. A gasket 8 is interposed between the shoulder 7 and the bottom .Y of the socket 5 and a retaining ring 9 bears Y of said electrode 10 having a nut or the like 12 for the attachment of Ithe current conducting wire, while the lower portion of this USpecication o1 Letters Patent.

Patented May 20, '1919.

. Application 1ed March 7, 1918.V Serial No. 220,987.

electrode extends into a bore 13 formed inl and opening through the lower end of the insulator 6.

In order for a plug of the type s0 far set forth to short circuit, provided the insulator remains intact, it is necessary for the current to flow from the shell 1 vdown the exterior of the insulator, around the lower edge of the latter, and upwardly along the wall of the bore 13 to the centralrelectrode 10, and in order to decrease the liability of such short circuiting, I lengthen the travel o-f the current by forming superimposed preferably- V-shaped grooves 14 in the wall of the bore 13. By this construction, instead of taking a straight course up the wall of the bore, the

current must zig-zag with the result that its travel is greatly increased. Before the current has time to travel over this long course and short circuit, it will jump across the gap between the electrodes 10 and 11 and fire the charge in the cylinder.

From the foregoing, taken in connection with the accompanying drawing, it will be obvious that although my invention is o-f extremely simple and inexpensive nature, it will be lhighly eflicient for preventing short circuiting, and since probably the best results are obtained from the several details shown and described, these features are preferably employed, but within the scope of the invention as claimed, numerous minor changes may well be made. Also, I wish it understood that any suitable material may be employed in the manufacture 'of the device and that it may be made in any of theV wel-l known standard sizes or in additional Vsaid socket, said insulator depending from said head into said shell, substantially to the lower end of the latter and in spaced relation. with the shell wall, said insulator hav ing a longitudinal bore leading fromV its lower end wall into said head, 'the wall of Said bore having, superirnposed V-shaped my hand in the presence of two subscribing grooves giving thereto a zig-zag formation Witnesses.

free of horizontal surfaces, an electrode secured in said insulator and extending 'MALLORY 5 through said bore, and a ground elect-rode 1 Witnesses: Y l extending from said shell. Y e W. H. PURDY,

In testimonyV whereof I have hereunto set C. C, BOWEN.

Copies of this patent may be obtained for vewcents each, by agdressig the Commissioner of Patents,

' Washington, D. G. 

